M1 said that it has fully restored its fibre broadband connections about an hour after it posted on Facebook that the service was down.
At around 1pm, M1 said: "We noted no data traffic on our fixed network on one of our domain name servers and immediately took action to redirect traffic and restore services to affected customers."
The telco also said services have been fully restored, advising affected customers to reset their optical network terminating (ONT) equipment.
M1 has in recent years grown its share of fibre broadband customers in. It had 90,000 such customers in the first quarter of this year, up from 30,000 a year ago.
This latest service interruption comes a week after M1 rivals Singtel was fined $6 million - the largest penalty ever for a telco - over a blaze at its Bukit Panjang Internet exchange last year that took down phone lines, banking, payment and Internet services across Singapore.